Introducing The Power Score

Introduction:

The goal for all athletes is to be their best. But what does “your best” actually mean? Most disciplines of Cycling require an athlete to have multiple well-developed abilities that are specific to that type of cycling. And even within a given discipline, there can be event-specific conditions that require athletes to tailor their training to meet those demands (for example, flat versus mountainous road races). As you can see, defining “your best” is always a moving target. To address this, we’ve developed the Power Score™. Power Score allows you to visualize the relationship between your range of abilities, as well as see where your current abilities rank in your athletic history. Below, we’ll give a deeper definition of the Power Score and we will discuss some examples for how it’s used.

Defining Power Score:

When exploring a rider’s range of abilities, the first visual reference we can think of is the Power Decay Curve™ (Fig. 1), which is the literal embodiment of your complete range of maximum wattages for any given length of time. Within Enfusion, the Power Decay Curve is built out of the highlights of the last 2-months of racing and training. However, what we can’t see from an individual Power Decay Curve is where the current curve ranks within your overall training history. In other words, are you in the best shape of your life, or are you struggling? Perhaps more importantly, we can’t tell whether you can put all of these abilities together on any given day. For example, can you produce your best 1-hour power and still do your best sprint? That’s where the Power Score comes in.

Figure 1. The Power Decay Curve models your maximum power you can sustain (y-axis) in Watts for the given length of time (x-axis).

The Power Score is a composite of 6 timepoints: 1-second (overall max wattage), 30-second, 1-minute, 4-minute, 20-minute, and 1-hour. These points were chosen, in part, because they are familiar (and meaningful) to most athletes/coaches, and because they are far enough apart from each other on the Power Decay Curve to allow us characterize the overall shape of the curve for that workout with a single value. For a given ride, each time point used in the Power Score is shown as a percentage of its historical maximum (Fig. 2). In this example, the rider was within the top-15 percentile for 4 of the 6 time points, and within the top-8 percentile for max wattage and 1-hour power. The overall Power Score for this ride was 87.79, which is calculated by averaging the historical percentages for each time point together. Thus, with a range of 0-100, a Power Score of 100 would represent you’re at 100% of your best-ever abilities across all time points, a Power Score of 50 would represent you’re at half of your best-ever ability, and so on. Importantly, you’re Power Scores are “living numbers,” meaning that they are constantly updated as your abilities evolve. This allows us to maintain the historical context of each ride, making it easy to objectively identify periods of top-form versus periods when you weren’t at your best. This can be critical to identifying training regimens that resulted in significant gains, versus those that didn’t work so well. As you can see from this example, this ride was a significant test of this athlete’s ability and that the consistency of the 6-efforts shows his/her range of abilities was well-balanced.

Figure 2. Power Score™ allows riders to visualize their range of abilities following a formal test, or a difficult workout/race. Here, we see a Power Score from a workout where the athlete demonstrated his form was well balanced, as he was able to produce consistently high-ranking efforts across his entire range of physiology.

The purpose of Power Score is to be able to track changes in your performance range across time. In order to make a statement about your capabilities at the time of a given workout, we need to make sure that the workout was one that required significant effort. Therefore, we only calculate Power Scores for workouts with either a wattage percent effort or RPE > 80% (see Blog 1 for definitions of these metrics). Without these criteria, Power Scores would be calculated for easy workouts and you wouldn’t be able to see your true strength measured over time.

Incorporating the Radar Chart:

In addition to the overall Power Score, we have also found that understanding the relationships between the 6 types of efforts can be incredibly informative. In order to visualize these relationships, we use a radar chart. A radar chart is a graphical method to compare multiple features relative to the same starting point. In our case, each time point corresponds to a corner of the hexagon. The center of the radar chart equals 0 and the outer ring represents 100% of highest wattage ever produced for that length of time. Therefore, the relative distance of each data point from the center indicates the percentage of your max ability produced during that workout for each length of time. If we go around the hexagon and connect the 6 data points with a line (Fig 2., red line), we can visualize the similarities and differences among the 6 efforts. Looking at Figure 2, we can quickly visualize what is summarized in the table to the right — that this ride required the athlete to use nearly his full range of abilities.

Power Score in Action:

Now that we’ve described the components of the Power Score, let’s go over an example of how to use it. Figure 3 shows the results for 3 different workouts with nearly identical Power Scores. By looking at Power Score alone, we can see that each ride challenged the rider’s overall range of abilities similarly, with each ranking approximately 73% of the best they’ve ever done. However by looking at the corresponding radar charts for each ride, we can see that these nearly identical Power Scores are made up of very different components. In the leftmost radar chart, we see the rider’s hardest efforts came from both top-end (1-second/max wattage) and 1-hour power. In contrast, the middle radar chart shows the most significant efforts came from mid-range (4 and 20 minute power), with less of a contribution of top-end efforts. In the rightmost radar chart, we can see the the contribution of top-end efforts to the Power Score were largely negligible (1-second and 30-second efforts were 40% and 60% of the rider’s best, respectively), while the 1-hour power effort was at nearly 100%. Taken together, we can see how the Power Score and the radar chart together provide a tool to compare different types of efforts. That’s great, but how do we put this information to use? There are 3 scenarios: 1.) Formal testing, 2.) Post-event analysis, and 3.) identifying potential for top performances, which are discussed briefly below.

Figure 3. The 6 points of the radar chart represent distinct time points. The outside of the ring represents 100% of your highest wattage ever produced for the given amount of time. The Power Score in the center is the average of your percent power you produced across all 6 time points. These radar charts allow you quickly assess the power profile of your workout and give you insight into the current state of your form.

Formal Testing:

As we’ve said, the original intention of the Power Score was to give athletes and coaches a way to track changes in performance across time. One way to accomplish this is through formal testing, which allows us to control several variables, including the intention of riders to put forward their best effort. We’ll be the first to admit that doing a formal test of all 6 of these efforts is likely impractical for most of us (if not inhumane). However, a more reasonable test could be done for 5 of the 6 efforts, which would include the 1-second through 20-minute efforts, and exclude the 1-hour effort. However, you may have other event specific tests you need to conduct. Regardless of how you decide to construct your test, comparing the Power Score and radar charts from the same testing protocol over time will allow for an “apples to apples” comparison of gains/losses that maintain historical context. Don’t forget, all of your Power Scores are living numbers that are constantly updated as you get stronger. This drastically simplifies the identification of when you’re at your best and when you’re not.

Post-event analysis:

A second use of the Power Score is to discover how one type of event or workout might differ from another. For example, how do the demands of a 2-hour mountain bike race compare to a 1-hour cyclocross race? What are the similarities, and what are the key differences? The Power Score and the shape of the radar charts can tell you. More importantly, you can quickly identify your strengths and weakness across event types, so you can tailor your training accordingly. If we take another look at the rightmost radar chart from Figure 3, we can again see that the rider used only 40% of their 1-second power, but was at nearly 100% for 1-hour power. This would suggest that we don’t need to worry about doing sprint workouts. Instead we should probably focus on increasing 20-minute and 1-hour power, as gains here would clearly be useful to the athlete.

Identifying potential for top performance:

A third important use of the Power Score is in combination with the Enfusion Score to identify potential for top performances. It is well documented that training affects the athlete by increasing both fatigue and fitness simultaneously. This is a core principle of Banister’s foundational Impulse-Response Model. According to Banister, the fatigue impulse dissipates more quickly than the fitness impulse, which allows us to get stronger with proper training and recovery. However, as discussed in Blog 2, there are limitations to the application of Banister’s full model, as well as the simplified derivatives, which we call “stress balance” models. As discussed in Blog 2, the Enfusion Score is able to address many of the problems associated with “stress balance” models by using machine learning to describe when individual athletes are riding well, or not.

Alright, so how do we use Enfusion Score and Power Score to identify potential for good performances? Another way to think of the Enfusion Score is as a fatigue measurement. A Low Enfusion Score is indicative of building fatigue, whereas a high Enfusion Score is indicative of low fatigue. In contrast, the Power Score measures changes in physical ability, which can serve as a fitness measure. Now, if we track Enfusion Score and Power Score over time, we have a new, highly individualized and effective method to measure both the fatigue AND fitness impulses associated with training. Let’s take a look at a quick example.

Figure 4. By tracking Enfusion Score and Power Score over time, we can identify an athlete’s performance potential. High Enfusion Score (i.e., low fatigue) and high Power Score (i.e., high fitness) indicates potential for top performance. Whereas low Enfusion Score (i.e., high fatigue) and low Power Score (i.e., low fitness) indicates low performance potential.

In this example, you can see that Enfusion Score (Fig. 4, Top) stays within the same relative range across time, regardless of how fit the athlete is. This is indicative of the accumulation and dissipation of fatigue through a normal training cycle. However, with the Enfusion Score alone we cannot tell if the athlete is responding to training. That’s where the Power Score comes in. First, we should note that the Power Scores in this example were derived from hard bouts of normal training, and are not formal testing. Therefore, it is reasonable to see fluctuation in the Power Score from ride to ride. Nonetheless, by looking at the Power Score over time (Fig. 4, bottom), we can see that the athlete maintains consistent performances through mid-February. At which point, we begin to see the Power Score increase through early March. On the last day of this example, we see the athlete had both a high Enfusion Score and a high Power Score. This suggests that the athlete had a great performance for this point in the season. A closer look at the athlete’s data shows that the athlete indeed broke a wattage record for total ride time. Taken together, we can see that the Power Score in combination with the Enfusion Score can identify periods of high versus low performance potential. We will go into greater detail on this subject, including some case studies, in our next blog post.

Putting it all together:

Taken together, the Power Score provides athletes and coaches with a new tool to measure the completeness of an athlete’s performance range. The Power Score can be used to track changes in performance across time during formal testing or just during normal training, and to to identify strengths/weaknesses across various event types. When used in combination with the Enfusion Score, the Power Score provides a powerful tool to identify periods of top performance potential. Importantly, the Power Score is a “living number” allowing for rapid identification of whether you’re getting stronger or missing the mark. We hope that you’ll consider the Power Score as one of the many tools to help you work toward your athletic goals.